#include <cstdio>
#include <cstring>
#include <vector>

using namespace std;

vector <int> g[10005];
int l[10005],r[10005],u[10005];


int pairup(int n)
{
    if (u[n]) return 0;
    unsigned int i;
    u[n]=1;
    for (i=0;i<g[n].size();++i)
        if (!r[i])
        {
            l[n]=i;
            r[i]=n;
            return 1;
        }
    for (i=0;i<g[n].size();++i)
        if (pairup(r[i]))
        {
            l[n]=i;
            r[i]=n;
            return 1;
        }
    return 0;
}

int main()
{
    int n,m,nr,ok,sol,x,y,i;
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);
    scanf("%d %d %d\n",&n,&m,&nr);
    for (i=1;i<=nr;++i)
    {
        scanf("%d %d",&x,&y);
        g[x].push_back(y);
    }
    for (ok=1;ok;)
    {
        ok=0;
        memset(u,0,sizeof(u));
        for (i=1;i<=n;++i)
            if (!l[i])
                ok|=pairup(i);
    }
    for (i=1;i<=n;++i)
        sol+=(l[i]>0);
    printf("%d\n",sol);
    for (i=1;i<=n;++i)
        if (l[i]>0)
            printf("%d %d\n",i,l[i]);
    return 0;
}